1. Field of the Invention
The present invention relates to a residual voltage regulating circuit for a Hall element, and more particularly to a residual voltage circuit for a Hall element improving dependency on temperature of the output voltage of the Hall element and secular changes of the element.
2. Description of the Prior Art
The large dependency on temperature of the Hall output voltage of Hall elements has conventionally hampered; the application of Hall elements to various field. The dependency on temperature of the Hall element was fundamentally controlled, to some extent, according to the material of the Hall element. Even Hall elements composed of germanium, indium and arsenic materials, which are said to have relatively good temperature characteristics, have temperature coefficients in the range of 0.03%/.degree. C. -0.1%/.degree. C., and therefore, were unsuitable for performing highly accurate measurements at working temperatures ranging from -20.degree. C. to +90.degree. C.
More specifically, the residual voltage generated during periods of zero magnetic field varied depending upon the change in temperture, and the voltage variations at the output terminals had an additive effect when measuring the magnetic field, thus producing in the inaccurate measurement.
In order to eliminate the above-mentioned problem, fixed resistance R, thermistor TH, and variable resistor (s) VR have been connected between the control current input terminals 2a and 2b of Hall element, and between the Hall voltage output terminals 3a and 3b, as shown in FIG. 1 (a) and FIG. 1 (b) in order to improve temperature dependence and reduce the residual output voltage when no magnetic field is applied to the element. In these external compensating circuits, in general, the positions of each variable resistor differed depending on that type of Hall element. In addition the values of fixed resistance R and thermistor TH had to be varied with the different types of Hall element materials. The above made re-biasing necessary whenever a Hall element having a different residual voltage during periods of zero magnetic field was substituted.